Phosphors

Abstract

One aspect of the present disclosure provides a phosphor wherein the main crystal phase has the same structure as an Li2MgGeO4 crystal phase, the phosphor includes tetravalent chromium as an activation element, and in a diffuse absorption spectrum, when X is the integrated value of the diffuse absorption spectrum over wavelengths of 330-430 nm and Y is the integrated value of the diffuse absorption spectrum over wavelengths of 600-800 nm, the value of Y / X is 3.8 or greater.

Description

[Technical Field]

[0001] This disclosure relates to phosphors. [Background technology]

[0002] Light-emitting devices, such as light-emitting diodes, are used in general lighting, backlights for liquid crystal displays, LED displays, and light-emitting devices for quality inspection. In LED displays, for example, a light-emitting device is used that has a light-emitting element that emits blue light and a wavelength converter that absorbs the primary light from the light-emitting element and emits light of a different wavelength. Various phosphors such as red phosphors and green phosphors are used as the wavelength converter.

[0003] Since near-infrared light can also be used as a heat source, research is underway on phosphors that emit light in the near-infrared region. Among the phosphors that emit light in the near-infrared region, those with chromium as the emission center have been proposed as candidates. For example, Patent Document 1 discloses a near-infrared emitting phosphor containing an oxide with a chemical composition in which, with a total molar ratio of Gd to Cr of 1 per mole, the molar ratio of Cr is 0.0085 or more and 0.05 or less, and which is excited by light having an emission peak wavelength in the range of 380 nm to 480 nm and has an emission peak wavelength in the range of 690 nm to 790 nm.

[0004] Furthermore, Patent Document 2 discloses a light-emitting device comprising a light-emitting light source and a phosphor, wherein the phosphor contains at least a near-infrared light-emitting phosphor that emits near-infrared light when excited. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-041135 [Patent Document 2] Japanese Patent Publication No. 2020-188044 [Overview of the project] [Problems that the invention aims to solve]

[0006] A phosphor that emits near-infrared light and exhibits excellent emission intensity would be useful.

[0007] This disclosure aims to provide a phosphor with excellent luminescence intensity. [Means for solving the problem]

[0008] This disclosure provides the following [1] to [7].

[0009] [1] The main crystalline phase has the same structure as the Li2MgGeO4 crystalline phase, It contains tetravalent chromium as an activating element, A phosphor in which, in its diffuse absorption spectrum, the integral value of the diffuse absorption spectrum with wavelengths of 330-430 nm is X, and the integral value of the diffuse absorption spectrum with wavelengths of 600-800 nm is Y, and the value of Y / X is 3.8 or greater. [2] The main crystal phase is given by the general formula: A2B(C 1-x Cr x It is represented as )O4 (where A, B, and C represent different metallic elements in the general formula), The phosphor according to [1], wherein the Cr content is 8 mol% or less based on the total amount of C and Cr. [3] The phosphor according to [2], wherein the Cr content is 6 mol% or less. [4] The phosphor according to [2] or [3], wherein A in the general formula contains Li, and the Li content in A is 90 mol% or more. [5] The phosphor according to any one of [2] to [4], wherein B in the general formula contains Mg, and the Mg content in B is 90 mol% or more. [6] A phosphor according to any one of [2] to [5], wherein C in the general formula contains Ge, and the Ge content in C is 90 mol% or more. [7] A phosphor according to any one of [1] to [6], wherein in the powder X-ray diffraction pattern, the value of α / β is 0.047 or less, where α is the maximum value of the peak intensity in the region where the diffraction angle (2θ) is 17.0 to 19.5° and β is the maximum value of the peak intensity in the region where the diffraction angle is 20.5 to 23.5°.

[0010] One aspect of this disclosure is to provide a phosphor in which the main crystalline phase has the same structure as the Li2MgGeO4 crystalline phase, contains tetravalent chromium as an activating element, and in the diffuse absorption spectrum, when X is the integral value of the diffuse absorption spectrum with wavelengths of 330 to 430 nm and Y is the integral value of the diffuse absorption spectrum with wavelengths of 600 to 800 nm, the value of Y / X is 3.8 or more.

[0011] The above-mentioned phosphor can exhibit excellent emission intensity because the ratio of integrated intensities in a specific wavelength range in the diffuse absorption spectrum is within a predetermined range. In the diffuse absorption spectrum, the peak observed in the 330-430 nm wavelength range corresponds to the absorption of hexavalent chromium, and the peak observed in the 600-800 nm wavelength range corresponds to the absorption of tetravalent chromium. A Y / X value greater than or equal to a predetermined value indicates a high proportion of tetravalent chromium in the phosphor.

[0012] The above main crystal phase is given by the general formula: A2B(C 1-x Cr x It is represented as O4 (wherein A, B, and C represent different metallic elements), and the Cr content may be 8 mol% or less (corresponding to x being 0.08 or less in the above general formula) or 6 mol% or less, based on the total amount of C and Cr.

[0013] In the above general formula, A may contain Li, and the Li content in A may be 90 mol% or more. Also, in the above general formula, B may contain Mg, and the Mg content in B may be 90 mol% or more. Also, in the above general formula, C may contain Ge, and the Ge content in C may be 90 mol% or more.

[0014] When the above phosphor is in the powder X-ray diffraction pattern, the value of α / β may be 0.047 or less, where α is the maximum peak intensity in the region where the diffraction angle (2θ) is 17.0 to 19.5°, and β is the maximum peak intensity in the region where the diffraction angle is 20.5 to 23.5°.

Advantages of the Invention

[0015] According to the present disclosure, a phosphor excellent in luminous intensity can be provided.

Brief Description of the Drawings

[0016] [Figure 1] FIG. 1 is a diagram showing the diffuse absorption spectrum of the phosphor prepared in the examples. [Figure 2] FIG. 2 is a diagram showing the powder X-ray diffraction spectrum of the phosphor prepared in the examples. [Figure 3] FIG. 3 is a diagram showing the measurement results of the luminous intensity of the phosphor prepared in the examples.

Modes for Carrying Out the Invention

[0018] Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition. The "steps" in this specification may be steps independent of each other or steps performed simultaneously.

[0019] One embodiment of the phosphor has the same structure as the Li2MgGeO4 crystal phase as the main crystal phase and contains tetravalent chromium as an activating element. The above main crystal phase has the general formula: A2B(C 1-x Cr x)It may be represented by O4. In the above general formula, A, B, and C represent different metal elements from each other. In the above general formula, A, B, and C are mainly intended to be each one kind of element, but a part thereof may be substituted and may represent two or more kinds of elements. In the above general formula, preferably, A is lithium (Li), B is magnesium (Mg), and C is germanium (Ge), but a part of each element may be substituted by an element that is a candidate for A, B, and C shown below.

[0020] In the above general formula, A may be, for example, lithium (Li), sodium (Na), potassium (K), etc., preferably contains Li, more preferably contains 90 mol% or more of Li, and particularly preferably is Li. In the above general formula, B may be, for example, magnesium (Mg), zinc (Zn), calcium (Ca), etc., preferably contains Mg, more preferably contains 90 mol% or more of Mg, and particularly preferably is Mg. In the above general formula, C may be, for example, germanium (Ge), silicon (Si), tin (Sn), etc., preferably contains Ge, more preferably contains 90 mol% or more of Ge, and particularly preferably is Ge. In the above general formula (C 1-x Cr x ) The notation means that both C and Cr are included, and it means that Cr is included in a form that substitutes a part of the site of C. In the phosphor, more specifically, when C is Ge, chromium (Cr) may be introduced into the germanium (Ge) site. In this case, the phosphor may be represented by, for example, the general formula: Li2Mg(Ge 1-x Cr x )O4. In the above general formula, x may be, for example, more than 0 and 0.1 or less, 0.005 to 0.1, 0.005 to 0.08, 0.005 to 0.06, 0.005 to 0.03, or 0.005 to 0.02. In the above phosphor, the main crystal phase has the same crystal structure as the Li2MgGeO4 crystal phase, and its space group may be, for example, Pmn21.

[0021] In this specification, the principal crystalline phase means the phase with the highest proportion of generated phases, as calculated by powder X-ray diffraction. In addition to the principal crystalline phase, the phosphor may also contain other phases to the extent that it does not impair the spirit of this disclosure. Examples of other phases include phases with the same crystal composition but different space groups (e.g., a crystal structure with a Pnma space group), or phases with different crystal compositions (e.g., MgCr2O4).

[0022] The crystalline structure of a phosphor can be confirmed by powder X-ray diffraction. Furthermore, the content of lithium (Li), magnesium (Mg), germanium (Ge), and chromium (Cr) in the phosphor's composition can be determined by preparing a sample solution through pressurized acid decomposition of the sample material, and then performing quantitative analysis using an ICP emission spectrometer. The oxygen (O) content can be estimated based on the charge balance from the elemental content of the ICP. Since the elemental composition of a phosphor corresponds to the proportion of each element used in its manufacture, the elemental composition of the phosphor can also be estimated from the raw material composition.

[0023] The chromium content in the above main crystal phase can be adjusted according to the luminescence characteristics required for the phosphor. The above main crystal phase is of the general formula: A2B(C 1-x Cr x When the main crystal phase is represented by the general formula A2B(C), the Cr content may be, for example, 10 mol% or less, 8 mol% or less (corresponding to x being 0.08 or less in the above general formula), 7 mol% or less, 6 mol% or less, 5 mol% or less, 2 mol% or less, or 1.5 mol% or less, based on the total amount of C and Cr. Increasing the chromium content may lead to the generation of a different phase during the manufacturing process, so keeping the upper limit of the chromium content within the above range can reduce the proportion of the different phase and improve the optical properties of the resulting phosphor. 1-x Cr xWhen expressed as )O4(A, B, C represent different metallic elements), the Cr content may be, for example, 0.3 mol% or more, 0.5 mol% or more, or 0.7 mol% or more, based on the total amount of C and Cr. Among the chromium solid-dissolved in the main crystal phase, tetravalent Cr (Cr 4+ ) is the element that forms the emission center, and by keeping the lower limit of the chromium content within the above range, the abundance of tetravalent chromium can be increased, and the emission intensity of the resulting phosphor can be more sufficiently improved. The chromium content in the above main crystal phase may be adjusted within the above range, and the above main crystal phase is of the general formula: A2B(C 1-x Cr x When represented as O4 (wherein A, B, and C represent different metallic elements in the general formula), the Cr content may be, for example, 0.3 to 10 mol% or 0.5 to 1.5 mol% based on the total amount of C and Cr.

[0024] The above-mentioned phosphor has a diffuse absorption spectrum in which, when X is the integral value of the diffuse absorption spectrum with wavelengths of 330 to 430 nm and Y is the integral value of the diffuse absorption spectrum with wavelengths of 600 to 800 nm, the value of Y / X is 3.8 or higher.

[0025] The lower limit of the above Y / X value may be, for example, 3.9 or higher, 4.0 or higher, or 4.5 or higher. By the lower limit of the above Y / X value being within the above range, tetravalent chromium (Cr 4+ A higher proportion of tetravalent chromium allows for improved luminescence intensity. The upper limit of the above Y / X value may be, for example, 8.0 or less, 7.5 or less, 7.0 or less, 6.5 or less, 6.0 or less, 5.5 or less, 5.3 or less, or 5.0 or less. A large Y / X value means a high proportion of tetravalent chromium, but increasing the proportion of chromium during manufacturing to increase the proportion of tetravalent chromium tends to increase the proportion of heterogeneous phases. Therefore, by setting the upper limit of the above Y / X value within the above range, it is possible to suppress the increase in the proportion of heterogeneous phases during the manufacturing process and produce a phosphor with superior optical properties. The above Y / X value may be adjusted within the above range, for example, 3.8 to 8.0, or 4.5 to 5.3.

[0026] In this specification, the integral values ​​X and Y of the diffuse absorption spectrum peaks refer to pseudo-absorption spectra calculated from the diffuse spectrum measured using an ultraviolet-visible spectrophotometer for the phosphor, i.e., values ​​determined from the diffuse absorption spectrum. The diffuse absorption spectrum is specifically obtained by measuring it using the procedure described in the examples of this specification. As the ultraviolet-visible spectrophotometer, for example, the "V-550" (product name) manufactured by JASCO Corporation can be used.

[0027] It is desirable that the content of heterologous phases in the above-mentioned phosphor be low. Among the heterologous phases, MgCr2O4 is generally black and can absorb the excitation light irradiated onto the phosphor and the fluorescence emitted, so it is particularly desirable to reduce its content. In the powder X-ray diffraction pattern, MgCr2O4 shows a peak in the region where the diffraction angle (2θ) is 17.0 to 19.5°, and Li2MgGeO4 has a peak in the region where the diffraction angle is 20.5 to 23.5°. Therefore, in the above-mentioned phosphor, the value of α / β can be adjusted to be low, where α is the maximum value of the peak intensity in the region where the diffraction angle (2θ) is 17.0 to 19.5° in the powder X-ray diffraction pattern, and β is the maximum value of the peak intensity in the region where the diffraction angle is 20.5 to 23.5°. The upper limit of the above α / β value may be, for example, 0.047 or less, 0.045 or less, 0.040 or less, 0.038 or less, or 0.035 or less. The emission intensity of the phosphor can be further improved by keeping the upper limit of the α / β value within the above range. The lower limit of the α / β value is not particularly limited and may be 0 (meaning it does not contain MgCr2O4), but may be, for example, 0.020 or higher, 0.030 or higher, or 0.032 or higher. Better emission intensity can be expected by keeping the lower limit of the α / β value within the above range. The α / β value may be adjusted within the above range, for example, 0.020 to 0.047, 0.032 to 0.038, or 0.030 to 0.035.

[0028] In this specification, the maximum values ​​α and β of the peak intensity refer to values ​​determined by powder X-ray diffraction analysis of the phosphor. The powder X-ray diffraction pattern is specifically determined by the procedure described in the examples of this specification.

[0029] The phosphors described above may be used alone or in combination with other phosphors. Because the phosphors according to this disclosure exhibit excellent luminescence intensity, they are suitably used in light-emitting devices such as LEDs, and display devices, for example. For instance, the phosphors may be dispersed in a curing resin. In this case, the curing resin is not particularly limited; for example, a resin used as a encapsulating resin for light-emitting devices can be used.

[0030] An example of a light-emitting device is a light-emitting element that emits primary light, and a wavelength converter that absorbs a portion of the primary light and emits secondary light having a wavelength longer than the wavelength of the primary light. The wavelength converter includes the phosphor described above according to this disclosure. The light-emitting element that emits primary light may be, for example, an InGaN blue LED. The light-emitting element and the wavelength converter may be dispersed in a encapsulating resin or the like.

[0031] The phosphors described above can be manufactured, for example, by the following method. One example of a method for manufacturing phosphors includes the steps of: firing a composition containing a compound having lithium as a constituent element, a compound having magnesium as a constituent element, a compound having germanium as a constituent element, and a compound having chromium as a constituent element in air to obtain a calcined product (hereinafter also referred to as the calcination step); and reducing at least a portion of the chromium in the calcined product by heat treatment in a reducing atmosphere containing ammonia (hereinafter also referred to as the reduction step).

[0032] The above composition contains compounds that serve as sources of constituent elements for a phosphor, and includes compounds having lithium as a constituent element, compounds having magnesium as a constituent element, compounds having germanium as a constituent element, and compounds having chromium as a constituent element.

[0033] Compounds containing lithium (Li) as a constituent element may include, for example, carbonates, oxides, fluorides, oxyfluorides, chlorides, nitrides, and metals. Among the above compounds, it is preferable to include carbonates from the viewpoint of raw material stability and reaction promotion. The compound containing lithium (Li) as a constituent element may be lithium carbonate.

[0034] Compounds containing magnesium (Mg) as a constituent element may be, for example, oxides, fluorides, oxyfluorides, chlorides, nitrides, and metals. Among the above compounds, it is preferable to include oxides from the viewpoint of raw material stability and reaction promotion. Compounds containing magnesium (Mg) as a constituent element may be magnesium oxide.

[0035] Compounds containing germanium (Ge) as a constituent element may be, for example, oxides, fluorides, oxyfluorides, chlorides, nitrides, and metals. Among the above compounds, it is preferable to include oxides from the viewpoint of raw material stability and reaction promotion. Compounds containing germanium (Ge) as a constituent element may be germanium oxide.

[0036] Compounds containing chromium (Cr) as a constituent element may be, for example, oxides, fluorides, acid fluorides, chlorides, nitrides, and metals. Among the above compounds, it is preferable to include oxides from the viewpoint of raw material stability and reaction promotion. Compounds containing chromium (Cr) as a constituent element may be chromium oxide.

[0037] The chromium content in the above composition relative to the total amount of germanium and chromium is 8 mol% or less. The chromium content may be, for example, 0.3 to 8 mol%, 0.5 to 5 mol%, 0.5 to 2 mol%, or 0.7 to 1.5 mol% relative to the total amount of germanium and chromium in the above composition. By keeping the upper limit of the chromium content within the above range, the generation of different phases can be suppressed and the optical properties of the resulting phosphor can be improved. Furthermore, by keeping the lower limit of the chromium content within the above range, the amount of tetravalent chromium can be increased, and the luminescence intensity of the resulting phosphor can be improved more sufficiently.

[0038] The above composition may contain, in addition to compounds having lithium as a constituent element, compounds having magnesium as a constituent element, compounds having germanium as a constituent element, and compounds having chromium as a constituent element, other components. Examples of other components include compounds having sodium (Na) as a constituent element, compounds having zinc (Zn) as a constituent element, compounds having calcium (Ca) as a constituent element, compounds having strontium (Sr) as a constituent element, and compounds having silicon (Si) as a constituent element.

[0039] The above composition can be prepared by weighing and mixing each compound. The mixing may be done using either a dry or wet mixing method. A dry mixing method may involve mixing each component using, for example, a V-type mixer. A wet mixing method may involve preparing a solution or slurry by adding a solvent or dispersion medium such as water, mixing each component, and then removing the solvent or dispersion medium.

[0040] The heating temperature (firing temperature) in the firing process may be, for example, 800-1600°C, 900-1500°C, 1000-1400°C, or 1100-1300°C. The reaction can be promoted if the lower limit of the heating temperature is within the above range. Furthermore, the volatilization of raw material components can be suppressed if the upper limit of the heating temperature is within the above range.

[0041] The heating time (baking time) in the firing process may be, for example, 3 to 11 hours, 4 to 10 hours, 5 to 9 hours, or 6 to 8 hours. The lower limit of the heating time being within the above range promotes the reaction. The upper limit of the heating time being within the above range suppresses the volatilization of the raw material components.

[0042] In this specification, firing time, heating time, etc., refer to the time (holding time) during which the ambient temperature of the object reaches a predetermined temperature and is maintained at that temperature. The rate of heating up to the predetermined temperature and the rate of cooling down to room temperature can be adjusted as appropriate. The rate of heating up in the firing process may be, for example, 2 to 15°C / min, 5 to 12°C / min, or 8 to 10°C / min. The rate of cooling down in the firing process may be, for example, 2 to 15°C / min, 5 to 12°C / min, or 8 to 10°C / min.

[0043] The firing process is carried out under open air.

[0044] The number of heat treatments in the firing process may be one, but may be two or more, for example, two to five times, or two to four times.

[0045] In the firing process, if multiple heat treatments are performed, they may be sequentially referred to as the first heat treatment, the second heat treatment, etc., and each heat treatment process may be sequentially referred to as the first firing process, the second firing process, etc. If the firing process involves two or more heat treatments, the heating temperature, heating time, atmosphere during heating, and pressure during heating for the first firing process may be the same as those for the heating processes described above. The heating temperature, heating time, atmosphere during heating, and pressure during heating for the second firing process and subsequent processes may be the same as or different from those for the first firing process. However, even if the heating temperature, heating time, atmosphere during heating, and pressure during heating for the second firing process and subsequent processes differ from those for the first firing process, they must remain within the range of the conditions described above for the heating processes.

[0046] In the reduction process, the calcined product prepared in the calcination process described above is heat-treated in a reducing atmosphere. By performing the reduction treatment, at least a portion of the chromium whose valence increased during the process of obtaining the calcined product can be reduced, thereby increasing the proportion of tetravalent chromium that contributes to luminescence.

[0047] The reducing atmosphere in the reduction process may contain, in addition to ammonia, hydrocarbons, carbon monoxide, and hydrogen, for example. Having such a reducing atmosphere can further promote the reduction of chromium. From the viewpoint of suppressing the presence of hexavalent chromium due to insufficient reduction of chromium in the reduction process, the reducing atmosphere is preferably an ammonia atmosphere.

[0048] The flow rate of the atmosphere in the reduction process may be, for example, 0.001 to 2.5 mL / min, 0.1 to 2.0 mL / min, 0.5 to 1.5 mL / min, or 0.8 to 1.2 mL / min when using a furnace tube with an inner diameter of 70 mm.

[0049] The heating temperature in the reduction process may be, for example, 300-1100°C, 400-1000°C, 500-900°C, or 600-800°C. By keeping the lower limit of the heating temperature within the above range, the proportion of pentavalent and hexavalent chromium can be reduced. Furthermore, by keeping the upper limit of the heating temperature within the above range, the proportion of trivalent chromium can be reduced.

[0050] The heating time in the reduction process may be, for example, 2 to 11 hours, 3 to 10 hours, 4 to 9 hours, or 6 to 7 hours. By keeping the lower limit of the heating time within the above range, the proportion of pentavalent and hexavalent chromium can be reduced. Furthermore, by keeping the upper limit of the heating time within the above range, the proportion of trivalent chromium can be reduced.

[0051] The heating rate in the reduction process may be, for example, 2-15°C / min, 5-12°C / min, or 8-10°C / min. The cooling rate in the reduction process may be, for example, 2-15°C / min, 5-12°C / min, or 8-10°C / min.

[0052] The above-described manufacturing method may include other steps in addition to the calcination and reduction steps. Examples of other steps include a grinding step, a classification step, and an acid treatment step.

[0053] The grinding step may be, for example, a step of grinding the calcined product obtained in the calcination step or the heat-treated product obtained in the reduction step. For example, by grinding the calcined product obtained in the calcination step before sending it to the reduction step to adjust the particle size, the surface area of ​​the calcined product can be increased, thereby improving the efficiency of reduction in the subsequent reduction step. Also, by grinding the heat-treated product obtained in the reduction step, the phosphor can be adjusted to a particle size according to its application.

[0054] In the grinding process, a general-purpose grinder or crusher can be used. For example, a mortar and pestle, ball mill, vibratory mill, and jet mill can be used. In this specification, "grinding" also includes "crushing".

[0055] Although several embodiments have been described above, this disclosure is not limited in any way to the embodiments described above. Furthermore, the descriptions of the embodiments described above are applicable to each other. [Examples]

[0056] The contents of this disclosure will be described in more detail below with reference to examples and comparative examples. However, this disclosure is not limited to the following examples.

[0057] (Example 1) <Method for manufacturing phosphors> Lithium carbonate (Li2CO3, manufactured by Kojun Chemical Laboratory Co., Ltd.), magnesium oxide (MgO, manufactured by Kanto Chemical Co., Ltd.), germanium oxide (GeO2, manufactured by Kojun Chemical Laboratory Co., Ltd.), and chromium oxide (Cr2O3, manufactured by Kojun Chemical Laboratory Co., Ltd.) were measured out into a container in a molar ratio of Li:Mg:Ge:Cr of 2:1:0.995:0.005, and the composition (raw material powder) was obtained by dry mixing.

[0058] 6.0 g of the above composition was weighed onto an alumina board and placed in a vertical furnace. Next, under atmospheric pressure, the temperature inside the vertical furnace was raised from room temperature at a rate of 10°C / min until it reached 1200°C, and then maintained at that temperature for 7 hours (calcination process). After that, heating was stopped and the mixture was allowed to cool to room temperature. After cooling to room temperature, the lump was collected from the container. The collected lump was crushed and pulverized in an alumina mortar, and then passed through a sieve with a mesh size of 150 μm to obtain a powdered calcined product as a sieved product.

[0059] Next, 2.5 g of the aforementioned powdered calcined material was weighed onto an alumina board and placed in a tubular furnace. Then, under an ammonia atmosphere, the temperature inside the tubular furnace was raised from room temperature at a rate of 10°C / min until it reached 700°C, and then maintained at that temperature for 6 hours to perform the heat treatment (reduction process). After that, the heating was stopped and the material was allowed to cool to room temperature. After cooling to room temperature, the lump was collected from the container. The collected lump was crushed and pulverized in an alumina mortar, and then passed through a sieve with a mesh size of 150 μm to obtain a powdered heat-treated material as a sieved product. This heat-treated material was used as the phosphor for Example 1. The obtained phosphor has the general formula: Li2Mg(Ge 1-x Cr x It was shown as O4 (x = 0.005), and it was confirmed that the main crystalline phase has the same structure as the Li2MgGeO4 crystalline phase.

[0060] (Example 2) A phosphor was obtained in the same manner as in Example 1, except that the mixing ratio in the above composition was changed so that the molar ratio of Li:Mg:Ge:Cr was 2:1:0.99:0.01.

[0061] (Example 3) A phosphor was obtained in the same manner as in Example 1, except that the mixing ratio in the above composition was changed so that the molar ratio of Li:Mg:Ge:Cr was 2:1:0.98:0.02.

[0062] (Example 4) A phosphor was obtained in the same manner as in Example 1, except that the mixing ratio in the above composition was changed so that the molar ratio of Li:Mg:Ge:Cr was 2:1:0.96:0.04.

[0063] (Example 5) A phosphor was obtained in the same manner as in Example 1, except that the mixing ratio in the above composition was changed so that the molar ratio of Li:Mg:Ge:Cr was 2:1:0.95:0.05.

[0064] (Comparative Example 1) A phosphor was obtained in the same manner as in Example 1, except that the mixing ratio in the above composition was changed so that the molar ratio of Li:Mg:Ge:Cr was 2:1:0.92:0.08.

[0065] (Comparative Example 2) A phosphor was obtained in the same manner as in Example 1, except that the mixing ratio in the above composition was changed so that the molar ratio of Li:Mg:Ge:Cr was 2:1:0.9:0.1.

[0066] (Comparative Examples 3-9) The powdered calcined products (before the reduction process) obtained in Examples 1-5 and Comparative Examples 1-2 were used as the phosphors for Comparative Examples 3-9, respectively.

[0067] (Comparative Example 10) A phosphor was obtained in the same manner as in Example 1, except that the reduction process was carried out in a high-temperature atmosphere furnace under the atmosphere of a mixed gas of nitrogen and hydrogen (a mixed gas in a volume ratio of nitrogen and hydrogen of 96:4 at standard conditions, containing hydrogen but a non-reducing atmosphere).

[0068] <Measurement of Cr content in phosphors> The phosphors obtained in Examples 1-5 and Comparative Examples 1-10 were subjected to quantitative analysis using an ICP emission spectrometer according to the method described later, and the Cr content was determined based on the total amount of Ge and Cr. The results are shown in Table 1.

[0069] [ICP Emission Spectroscopy Method] The composition was analyzed using a multi-type ICP emission spectrometer (Agilent, model number: 5110VDV). 10 mg of the phosphor was placed in a platinum crucible, 2 g of alkaline flux was added, and it was melted in an electric furnace. After cooling, 20 mL of hydrochloric acid (HCl) was added to the platinum crucible, and the mixture was heated and dissolved in a warm bath to obtain a solution. The obtained solution was then diluted to a final volume of 100 mL. This 100 mL solution was diluted 10-fold with pure water and used as a test solution. This solution was then set in the above-mentioned instrument, and its composition was analyzed.

[0070] <Measurement of the diffuse absorption spectrum of a phosphor> The phosphors obtained in Examples 1-5 and Comparative Examples 1-10 were subjected to diffuse absorption spectroscopy measurements according to the method described later. The integral values ​​of the diffuse absorption spectra obtained from these measurements—X for wavelengths of 330-430 nm and Y for wavelengths of 600-800 nm—were used to determine the Y / X ratio. The results are shown in Table 1 and Figure 1. Note that Figure 1 shows only some of the results for reference.

[0071] [Diffuse absorption spectrum measurement method] Using the ABSORBANCE mode of a UV-Vis spectrophotometer (manufactured by JASCO Corporation, product name: V-550), a pseudo-absorption spectrum was obtained from the diffusion spectrum of a sample packed in a quartz cell.

[0072] <Measurement of X-ray diffraction spectra of phosphor powder> The phosphors obtained in Examples 1 to 5 were further subjected to powder X-ray diffraction measurements according to the method described later. The value of α / β was determined using the maximum peak intensity α in the region where the diffraction angle (2θ) is 17.0 to 19.5° and the maximum peak intensity β in the region where the diffraction angle is 20.5 to 23.5°, both obtained from these measurements. The results are shown in Table 1 and Figure 2. Note that only some of the results are shown in Figure 2 for reference.

[0073] [Measurement of powder X-ray diffraction] The X-ray diffraction pattern of the sample was obtained using an X-ray diffractometer (manufactured by Rigaku Corporation, product name: Ultima IV). CuKα rays (characteristic X-rays) were used for the measurement.

[0074] <Evaluation of phosphors> The luminescence intensity of the phosphors obtained in Examples 1-5 and Comparative Examples 1-10 was measured according to the method described later. The results are shown in Table 1 and Figure 3. Figure 3 shows only some of the results for reference. The luminescence intensity was evaluated as a relative value based on the luminescence intensity of the phosphor in Example 1.

[0075] [Measurement of luminescence intensity] First, the phosphor to be measured was packed into a quartz cell and attached to the opening of an integrating sphere. Monochromatic light, spectrally separated to a wavelength of 676 nm from a xenon lamp (the light source), was introduced into the integrating sphere as excitation light for the phosphor using an optical fiber. This monochromatic excitation light was irradiated onto the phosphor to be measured, and the fluorescence spectrum was measured. A spectrophotometer (manufactured by HORIBA, Ltd., product name: Fluorolog-3-iHR-NIR) was used for the measurement. From the obtained fluorescence spectrum data, the intensity ratio was determined when the emission intensity of Example 1 was set to 1.0.

[0076] [Table 1] [Industrial applicability]

[0077] According to this disclosure, a phosphor with excellent luminescence intensity can be provided.

Claims

1. The main crystal phase is Li ２ MgGeO ４ Having the same structure as the crystalline phase, It contains tetravalent chromium as an activating element, In the diffuse absorption spectrum, if X is the integral of the diffuse absorption spectrum with wavelengths of 330 to 430 nm, and Y is the integral of the diffuse absorption spectrum with wavelengths of 600 to 800 nm, then the value of Y / X is between 4.5 and 5.

0. A phosphor in which, in a powder X-ray diffraction pattern, the value of α / β is 0.047 or less, where α is the maximum peak intensity in the region where the diffraction angle (2θ) is 17.0 to 19.5° and β is the maximum peak intensity in the region where the diffraction angle is 20.5 to 23.5°.

2. The main crystal phase is given by the general formula: A ２ B (C １－ｘ Cr ｘ ) O ４ (In the general formula, A, B, and C represent different metallic elements.) The phosphor according to claim 1, wherein the Cr content is 8 mol% or less based on the total amount of C and Cr.

3. The phosphor according to claim 2, wherein the Cr content is 6 mol% or less.

4. The phosphor according to claim 2 or 3, wherein A in the general formula contains Li, and the Li content in A is 90 mol% or more.

5. The phosphor according to claim 2 or 3, wherein B in the general formula contains Mg, and the Mg content in B is 90 mol% or more.

6. The phosphor according to claim 2 or 3, wherein C in the general formula contains Ge, and the Ge content in C is 90 mol% or more.

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